A Dynamic Triradical: Synthesis, Crystal Structure, and Spin Frustration

Abstract

Polyradicals, i.e., multispin organic molecules, are playing important roles in radical-based material applications for their spin−spin interaction. A dynamic covalently bonded multispin molecule may endow materials with added function such as memory and switching. However, such a species has yet to be reported. We here report the synthesis, characterization, and crystal structure of a dynamic triradical species. It is generated by the self-assembly of two molecules through a Lewis acid coupled electron transfer. The crystalline species is spin-frustrated without Jahn−Teller distortion at low temperature, while it dissociates back to diamagnetic starting material in solution at high temperature. The reversible process is tracked by variable-temperature NMR, EPR, and UV−vis−NIR spectroscopy. Isolation, property study, and dynamic bonding investigation on such a species lay the foundation for the design of functional polyradicals with potential application as memory or switching devices.

Electronic Structure and Transformation of Dinitrosyl Iron Complexes (DNICs) Regulated by Redox Non-Innocent Imino-Substituted Phenoxide Ligand

“…With the spin-frustrated framework of the isotropic Heisenberg–Dirac–van Vleck (HDVV) model (Figure S20c,d), the exchange parameters cannot be determined unequivocally, and the energy pattern for the isosceles triangle (C 2 ) includes the low-lying ground spin doublet ( 2 B 2 ), an excited spin doublet ( 2 A 1 ) at δ energy (δ = J 1 – J 2 ), and an excited spin quartet ( 4 A 2 ) at (3 J av + δ)/2 energy ( J av = (2 J 1 + J 2 )/3). The fitting of the magnetic data for an isosceles spin frustrated situation could be expressed by eq . − χ m = χ m ( { Fe ( NO ) 2 } 9 − { Fe ( NO ) 2 } 9 − [ · ON 2 Me ] 2 − ) + TIP = N β 2 g 2 4 k T ( cosh false( δ 2 k T false) + 5 exp false( 3 J av 2 k T false) cosh false( δ 2 k T false) + exp false( 3 J av 2 k T false) ) + TIP …”

Boron‐Nitrogen Lewis Pairs in the Assembly of Supramolecular Macrocycles, Molecular Cages, Polymers, and 3D Materials

“…Systems with P that involve FLP-type chemistries have already received much attention and, for example, oxygen-based quinone systems show exciting properties such as dynamic radical formation when combined with borane Lewis acids. [83] This leaves much room for new innovations and the development of functional materials with exciting and unprecedented properties.…”

Boron‐Nitrogen Lewis Pairs in the Assembly of Supramolecular Macrocycles, Molecular Cages, Polymers, and 3D Materials

“…Similarly, Lewis basic building blocks that contain other Group 15 and Group 16 elements are highly promising. Systems with P that involve FLP‐type chemistries have already received much attention and, for example, oxygen‐based quinone systems show exciting properties such as dynamic radical formation when combined with borane Lewis acids [83] . This leaves much room for new innovations and the development of functional materials with exciting and unprecedented properties.…”